Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines employ turbochargers to deliver compressed air for combustion in the engine. A turbocharger compresses air flowing into the engine, helping to force more air into the combustion chambers of the engine. The increased supply of air allows increased fuel combustion in the combustion chambers of the engine, resulting in increased power output from the engine.
A typical turbocharger includes a housing, a shaft, a turbine wheel attached to one end of the shaft, a compressor impeller connected to the other end of the shaft, and bearings to support the shaft. Exhaust from the engine expands over the turbine wheel and rotates the turbine wheel. The turbine wheel in turn rotates the compressor impeller via the shaft. The compressor impeller receives cool air from the ambient and forces compressed air into combustion chambers of the engine.
Bearings help to center the turbine wheel, the compressor impeller, and the shaft about an axis of rotation. An oil pump typically provides pressurized oil to lubricate the bearings. One or more seals help to prevent leakage of oil from a bearing housing surrounding the bearings into the turbine housing. The seals also help to prevent leakage of hot exhaust from the turbine housing into the bearing housing. Turbocharger seals often include a piston ring type arrangement in which a baffle extends radially inward from a bearing housing bore into an annular recess in an outer surface of the shaft. Imbalance in the turbine wheel or shaft can cause the baffle to dig into the shaft, causing damage to both the shaft and the bearing housing. Although the bearing housing and/or shaft can be repaired or replaced, such repairs can be expensive and may place the turbocharger out of service.
One attempt to address some of the problems described above is disclosed in U.S. Patent Application Publication No. 2013/0071243 A1 of Kocher et al. that published on Mar. 23, 2013 (“the '243 publication”). In particular, the '243 publication discloses a turbocharger rotating assembly that includes a shaft supported by a bearing. The '243 publication further discloses that the bearing is disposed in a sleeve inserted into the turbocharger housing. The '243 publication discloses that the sleeve has a lubricant passage for supplying lubricant to the bearing. The '243 publication also discloses a piston-ring seal arrangement in which the outer surface of the shaft has an annular groove that receives a seal component which has an outer surface located in close proximity to an inner wall of the sleeve.
Although the '243 publication discloses a sleeve member that supports the turbine bearing and provides an oil seal, the disclosed arrangement may still be less than optimal. For example, maintaining close proximity between the outer surface of the seal component and the inner wall of the sleeve may require tight control over dimensions, which may increase the manufacturing cost. Moreover, machining two separate bores in the sleeve to accommodate the bearing and provide the sealing feature may require changing fixtures during manufacturing, making it difficult to tightly control the concentricity of the sealing surface and the bearing. In addition, because the sleeve of the '243 publication is directly attached to the turbine housing, the sleeve may be exposed to very high temperatures due to the heat transferred from hot exhaust gases via the turbine housing to the sleeve. Exposure to high temperatures may degrade the performance of the bearing and may reduce the useful life of the bearing and the sleeve. The piston-ring seal arrangement of the '243 publication may also be insufficient to prevent oil leakage from the bearing into the turbine housing.
The turbine bearing and seal assembly of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.